Hi folks,
Please find attached my second re-write of the SMI detector, now called the
Hardware Latency Detector. This is a loadable module that grabs the CPU for
configurable periods of time (all under stop_machine()) and samples the TSC
looking for discontinuity. If observed latencies exceed a threshold (for
example caused by an System Management Interrupt or similar) then the
event is recorded in a global ring_buffer, readable via debugfs.
The previous version was too x86-centric, since there is no reason one could
not also use this newly renamed hwlat_detector on any supported platform with
some kind of underlying firmware/virtualization issues effecting observable
system latency measurements.
Thanks to akpm and others for feedback comments so far.
Changes since the previous version:
- Renamed to hwlat_detector
- Followed Andrew's cleanup advice
- Rewritten the documentation
Jon.